Electrolytic apparatus



March 29, 1932.

L. E. WARD ET AL ELECTROLYTIC APPARATUS Filed Aug. 5. 1927 2sneets-sneet INVENTORS 1.014215 5. Marc/ and 3 M T a;

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Patented Mar. 29, 1932 UNITED STATES PATENT OFFICE LOUIS E. WARD ANDRALPH M. HUNTER, OF MIDLAND, MICHIGAN, ASSIGNORS TO THE DOW CHEMICALCOMPANY, OF MIDLAND, MICHIGAN, A CORPORATION 01' MICHIGAN ELECTROLYTICAPPARATUS Application filed August 5, 1927.- Serial No. 210,785.-

The present improvements, relating as indicated to electrolyticapparatus, have more particular regard to an electrolytic cell forroducing a metal lighter than the electroyte, for example for producingmetallic magnesium from a bath of molten salts or compounds of suchmetal and specifically from magnesium chloride. In the operation of aso-called magnesium cell various difficulties are encountered due notonl to the fact that the metal is lighter than t e bath but also due tothe fact that such metal when highly heated i. e. in fluid state,readily ignites or burns upon exposure to the air. It

. isalso diflicult to collect the dispersed particle of the metal freefrom adhering electrolyte.

One object of the resent invention ac-. cordingly is to provi e anelectrolytic apparatus or cell so arranged as to permit the easy andconvenient addition of fresh raw material to the cell as well as thecollection and removal therefrom of the molten metal with minimum dangerof the latter being oxidized. A further object is to provide anapparatus or cell which may be constructed as a large unit, which willhave a considerably greater capacity than an such apparatus heretoforedesl ed, so ar as we are aware, and which Wlll be capable ofcontinuous'operation, i. e. without requiring to be shut downincidentally to charging raw material or removi metal product or evenfor replacing the car on electrodes employed as anodes in the cell. 7

To the accomplishment of the foregoing and related ends the inventionthen consists of the. means'hereinafter fully described and particularlypointed out in the claims,-the annexed drawings and the followingdescription illustrating but-one of the various ways in which theprinciple of the invention may a be carried out;

In said annexed drawin s:

Fig. 1 is a central vertical section of one form of our improvedelectrolytic apparatus, and specifically of a cell for the electrolyticproduction of magnesium; Fig. 2 is a plan view of such apparatus or cellwith certain of the superstructure removed; and Fig. 3 is acentralvertical section similar to that of Fig. 1, but looking in theopposite direction, as indicated b the broken line 3-1.

The composition of the bath to be electrolyzed will of course vary inthe first place with the metal which it is desired to produce and in thesecond place, articularly in the electrolytic production of magnesium,as is well known, several different salts or compounds are availablefrom which a selection may be made. The present apparatus while designedmore particularly for the electrolysis of magnesium chloride is, it willbe understood, adaptable for general use in thus producing so-calledlight metals from their chlorides or other compounds.

The molten bath is'contained in a metallic vessel 1, which, as shown inthe several figures of the drawings, preferably takes the form of arelatively shallow cast steel pot of approximately. circular form inplan, such vessel being provided with an outwardly directed flange 2about its upper edge, whereby the vessel may be supported on the walls 3of a suitable furnace chamber, such furnace being required to produceinitial fusion of the electrolyte,.or to warm up, in case of necessity,the contents of the pot.

At one point in its periplhery the sidewall of the pot is formed wit anintegral upwardly proiecting arm 4, through which electric current. maybe supplied to the pot by means of suitable connections, as will bepresently described, such pot serving as the main cathode member of thecell. Supported cen trally within the ot or vessel. is an openendedcylindrical s ell or curtain ring 5, that constitutes a suiplementalcathode member to the vessel. uch shell or ring 5 is provided with feet6, or equivalent means whereby it isheld in spaced relation from thebottom of the pot or vessel 1, so that the electrolyte may circulatefreely withinand about the shell, such feet being preferabl welded tothe ot bottom. The upper end 6 ring 5 is slightl y contracted so as toform a neck or well 7 of somewhat reduced diameter in which the moltenmetal may collect, such well rising above the level of the electrolytein vesrsel land being fitted with a removable cover of the pot and theouter surface of the ring form respectively the outer and inner activecathode surfaces of an enclosed annular ring shaped cell, in which alsoa plurality of anodes, as will presently be described, depend from aboveinto the electrolyte. In addition to the outwardly projecting flange 2the vessel 1 is provided with an inwardly directed flange 12 andsupported on the latter is an annular ring 14 of refractory material, aring 15 of similar material but of smaller diameter resting on theoffset portion of shell 5 formed by the necking in of the latter.Additional courses 16 and 17 of refractory material may be built uponsaid rings 14 and 15 to provide a support for an annular cover 18 thatcloses the portion of the pot or vessel 1 lying between the outer wallthereof, and the shell 5. This cover as best shown in Fig. 2 ispreferably composed of segmental sections 18 which are parted on linesintersecting the positions of the series of carbon electrodes 20 thatconstitute the anode members of the cell. The central opening left bysuch annular cover is adapted to be closed by a separate removable cover21 'located directly over the cover 8 on the cathode ring or shell 5. v

The number of carbon electrodes 20 will of course vary with the size ofthe cell, fourteen being employed in the particular one illustrated inthe drawings, such electrodes being supported so as to depend downwardlyinto the space between the outer wall of vessel 1 and the shell or ring5.

For the purpose of thus supporting the electrodes 20 a correspondingnumber of hanger rods 22 are vertically guided in a suitable frame 23supported at a suitable height above the cell-byposts 24, caps 25 ofinsulating material being interposed between such posts and frame sothat the latter will be thoroughly. insulated from the cell and avoidgrounding. The rods 22 at their lower ends are provided with clamps 26whereby they may be detachably secured to the adjacent ends of thecorresponding electrodes 20 and provision is made for raising andlowering the latter by means of a series of winches 27, one for each rodor electrode, such winches being connected with the several clamps 26through the medium of cables orchains 28. Each winch is independentlyoperable by means of worm gearing 28 and a detachable crank 29 so thatany selected electrode may be raised or lowered in order to cause such'electrode to depend the proper distance into vessel 1.

The electrical connections for the electrodes 20 include a commoncircular buss bar 30 that surrounds the rods 22, and flexible leads 31extending from such bar to the respective clamps 26. Only two such leadsare shown in Fig. 1, just as only one of the winches is there shown inorder not to confuse the drawings with unnecessary details.

It will be noted that the anodes 20 occupy a part only of'the annularspace, being disposed in a horseshoe shaped formation, soas to leave aspace 35 (see Fig. 2) that may be denominated a neutral zone. Theapproximate level of the electrolyte is shown by the line aa in Fig. 3.Metallic collecting rings 36 and 37 skirt the upper edges respectivelyof the outer and inner active cathode surfaces, these rings being ineffect parts of the inner and outer cathodes that depend. into the cellboth in the form of inverted troughs, adapted to catch and collect themetal risingthrough the bath from the cathode surfaces by gravity. Thesetroughs are connected by ports 38 and a duct 39 to the inner collectingwell 7, said ports and ducts being adapted to lead the metal from thecollecting troughs into the well, where it may accumulate to aconsiderable depth, enabling easy withdrawal at suitable intervals oftime. Cathodic action upon metallic surfaces above these collectingrings is restricted and practically prevented by the covering rings 14and 15, which as previously described may be of fire brick or othersuitable material and are fitted upon such surfaces thereby protectingthem from the action of the anolyte and anode products as well asreducing the flow of current and production of metal above thecollecting rings.

The covers 18 may be made from soapstone slabs or the like and areclosely fitted around the anodes as well as rest closely upon the brickor equivalent rings 16 and 17, thereby forming together with baflles 40and 41 that dip into the; electrolyte and cross the annular ring shapedspace between the ends of the neutral zone 35 (see Fig.2) and theends ofthe horseshoe shaped anode compartment, a closed anode gas trap abovethe electrolyte. Such trapped space is provided with an outlet 42through one of the covers suited for connection to a fine for drawingoif obnoxious or valuable gaseous anode products.

Cover 8, it will be noted, seals in the bath "and retains a reducingatmosphere above the pot at or near the center. The bath ma be stirredthrough this zone and opening i desired. The baflles 40 and 41 restrictcirculation of anolyte into this neutral zone 35.

In operation, electric current leaving the anodes passes from them tothe cathode surfaces in generally radial directions outwardly andinwardly, through the bath, liberate ing and depositing metal upon thevertical cathode surfaces. This metal as soon as it imcumulates insufliciently large droplets or films rises by reason of its low gravityand is caught in the collecting rings, from WhlCll it is led by the duct39 from the collecting ring 36 and the ports 38 from the collectin ring37 into the central metal collecting well The aseous anode products, asfor instance chlorine and hydrochloric acid (the latter if some water bepresent in the bath) are trapped as hereinbefore described and are ledoff for use or other disposal through the outlet 42. The'protectiverings covering the upper metal surfaces in contact with the anolyteprevent any substantial flow of current throu h the bath to suchsurfaces, thereby restrictmg the liberation of metal thereon to anegligible amount, and these rings also cover and protect those metalsurfaces from the corrosive action of the anolyte and anode products.

At suitable intervals, the covers 21 and 8 may be removed, access beingeasy thereto through the space between the'ends of the horseshoe shapedring of anodes and over the neutral zone 35, and the metal may be dippedout, tapped or drawn off by gravity or b suction through a pipe. Atother suitab e intervals, sludge or sediment may be withdrawn throughsuch neutral zone and, if the chloride fed to the cell be anhydrous,fresh electrolyte may be added therethrough. If, however, MgCl .H,(), orsimilar chloride containing water of crystallization be used, we

refer to feed it into the anode compartment in accordance with themethod specified in U. S. Letters Patent to Cottringer and Heath U. S.1,567,318, dated Dec. 29, 1225, covering use of hydrated feeds. The bathmay also be dipped out or drawn out through the neutralr zone. Ifdesired a notch 43 (see Fig. 3) may be left in the cathode ring 5adjacent to the neutral zone to make easier access of dipper to innerportions of the bath.

This cell will be found well adapted to the production of metals whichwill float upon a fused bath, the specific form illustrated beingadmirably suited to the production of metallic magnesium from a fusedchloride bath. This cell employs a cathode pot and central cathode ringinstead of the conventional cathode pot only. It further employs aplurality of anodes arranged in'a ring in the annular cell enclosedbetween the opposed cathode surfaces of the pot and ring, instead of thesingle central anode of the conventional cell. In this way possibleanode surface and working capacity relative to size and cost of cell arereatly increased, while at the same time a s ort path through the bath,ample cathode surface and low current densit are provided. Thesefeatures all tend to owervoltage and power. input per unit output.

Efi'ective conservation of the metal anolyte and anode product attackresults from provision made to lead it away promptly to a collect-ingwell, where it may stratify free from flux and in a deep layer enablingeasy removal at infrequent intervals and safe retention between times ofremoval; while in the neutral zone workable access is afforded to i. thecell for feeding, stirring if required, removal of bath .or sediment,observation, etc., during operation without requiring interferences withsame or making a nuisance through venting of noxious gases, or wastageof valuable heat.

Small modifications will permit use of the i neutral zone for a metalcollecting well, i. e. by directing the outlets from the collectingrings into same. We accordingly do not limit ourselves to exact detailsas shown or to strictly concentric or circular constructions, since manyof the advantages of the double cathode and .ring of anodes may beattained using rectangular, oval, triangular and other geometric orirregular forms, the circular form being, however, a convenient one.

Other modes of applying the principle of our invention may be employedinstead of the one explained, change being made as regards the mechanismherein disclosed, provided the means stated by any of the followingclaims or the equivalent of such stated means be employed.

We therefore particularly point out and distinctly claim 'as ourinvention 1. In an electrolytic apparatus for producing a metal lighterthan the electrotlye, the

combination of a vessel adapted to contain such electrolyte in.moltenstate, a cathode in the form of a ring supported in said vessel, saidring being arranged to permit free flow of the electrolyte around thelower edge thereof, and being further provided with ports in its upperportion permitting flow of molten metal from without into such portion,and a plurality of anodes depending into said vessel aroundsaid ring.

- 2. In an electrolytic apparatus for producing a metal lighter than theelectrolyte, the

combination of a vessel adapted to contain,

such electrolyte in molten state, a cathode in the form of a ringsupported in said vessel, said ring being arranged to permit free flowof the electrolyte around the lower edge thereof, and being furtherprovided exterlorly with a downwardly directed trough adjacent to itsupper end and with ports from such trough permitting flow of moltenmetal from without into such upper end, and a plurality of anodesdepending into said vessel around said ring.

3. An electrolytic cell including an outer cathode pot and an innercathode ring, and a plurality of anodes depending into the space betweensaid pot and ring, said anodes being omitted at one side to leave aneutral space and permit access to said ring.

4. An electrolytic cell including an outer cathode pot and an innercathode ring, and a lurality of anodes depending into the'space V etweensaid pot and ring, said anodes being omitted at one side to leave aneutral space and permit access to said ring, and the portion of suchspace wherein said anodes thus depend being sealed off to form a gastrap.

5. An electrolytic cell for producing a molten metal lighter than theelectrolyte, including an outer cathode pot and an inner cathode ring, aplurality of anodes depending into the space between said pot and ring,and means adapted to collect and conduct molten metal from the exteriorof said ring into the interior thereof. I

6. An el ctrolytic cell for producing a molten meta lighter than theelectrolyte, in-

eluding an outer cathode pot and an inner cathode ring, a plurality ofanodes depending into the space between said pot and ring, and meansadapted to collect and conduct molten metal from the collecting troughsadjacent the interior wall of said pot and the exterior wall of saidring, respectively, into the interior of said ring. l

7. An electrolytic cell including an outer cathode pot and an innercathode ring, a plurality of anodes depending into the space betweensaid pot and ring, and a protective covering for the upper portions of.the pot and ring surfaces facing said anodes.

8. In an electrolytic apparatus for producing a metal lighter than theelectrolyte, the combination of a vessel adapted to contain suchelectrolyte in molten state and constituting the main cathode member, asupplemental cathode in the form of a ring supported in said vessel inspaced relation to the bottom thereof, a plurality of anodes dependinginto said vessel around said ring, common electrical connections forsaid vessel and ring, and

' mental cathode in the form of a ring supported in said vessel inspaced relation to the bottom thereof, said ring having, its upperportion ofgreduced diameter whereby a well is formed for collection ofmolten metal, a plurality of anodes depending into said vessel 4 aroundsaid ring, common electrical connecanon electrical connections for saidanodes.

10. In an electrolytic apparatus for producing a metal lighter than theelectrolyte, the combination of a vessel adapted to contain suchelectrolyte in molten state and constituting the main cathode member, asupplemental cathode in'the form of a ring supported in said vessel inspaced relation to the bottom thereof, said ring having its upperportion of reduced diameter whereby a well is formed for collection ofmolten metal and being further provided with ports adjacent such portionof reduced diameter permitting flow of such metal into such well, aplurality of anodes depending into said vessel around said ring, commonelectrical connections for said vessel and ring,'and other commonelectrical connections for said anodes.

all. In anelectrolytic apparatus for producing a metal lighter than theelectrolyte, the combination of a vessel adapted to contain suchelectrolyte in molten state and constituting the main cathode member, asupplemental cathode in the form of a ring supported in said vessel inspaced relation to the bottom thereof, said ring having its upperportion of reduced diameter-whereby a well is formed for collection ofmolten metal and being further provided exteriorly with'a downwardlydirected trough adjacent such portion of reduced diameter and with portsfrom such trough permitting flow of such metal into such well, aplurality of anodes depending into said vessel around said ring,

common electrical connections 'for said vessel and ring, and othercommon electrical connections for said anodes.

12. In an electrolytic apparatus for producing a metal lighter than theelectrolyte,

the combination of a vessel adapted to contain such electrolyte inmolten state and constituting the main cathode member, a sup-. plementalcathode in the form of a ring supported in said vessel in spacedrelation to the bottom thereof, said ring having its upper portion ofreduced .diameter whereby a well is formed for collection of moltenmetal and being further provided exteriorly with a downwardly directedtrough adjacent such portion of reduced diameter and with ports fromsuch trough permitting flow of such metal into such well, a similartrough provided interiorlv of said vessel adjacent its upper end, a ductleading from such lastmentioned trough to such well, a plurality ofanodes depending into said vessel around said ring, common electricalconnections for said vessel and ring, and other common electricalconnections for said anodes.

13. In an electrolytic apparatus for producing a metal lighter than theelectrolyte, the combination of a'vessel adapted to contain suchelectrolyte in molten state, a cathode in the form of a ring supportedin said the combination of a Vessel adapted to con-,

, depending through said cover into said vessel around said ring, and aseparate centrally located cover for said vessel directly over saidring.

14. In an electrolytic apparatus for pro-' ducing a metal lighter thanthe electrolyte,

the combination of a vessel adapted to contain such electrolyte inmolten state, a cathode in the form of a ring supported in said vessel,said ring being arranged to permit free flow of the electrolyte aroundthe lower edge thereof, an annular cover over the portion ofsaid vesselbetween the outer wall thereof and said ring, a plurality of anodesdepending through said cover into said vessel around said ring, aseparate centrally located cover for said vessel directly over saidring, and an independent cover for the latter. 15. In an electrolyticapparatus for producing a metal lighter than the electrolyte,

tain such electrolyte in molten state, a cathode in the form of a ringsupported in said vessel, said ring being arranged to permit free do ofthe electrolyte around the lower edge thzi'eof, an annular cover overthe portion of said vessel between the outer wall thereof and said ring,and a plurality of anodes depending through said cover into said vesselaround said ring, said cover comprising segmental sections parted online with said anodes, respectively.

16. In an electrolytic apparatus for producing .a metal lighter than theelectrolyte, the combinationof a vessel adapted to contain suchelectrolyte in molten state and constituting the main cathode member. asupplemental cathode in'the form of a ring supported in said vessel inspaced relation to the bottom thereof, a plurality of anodes dependinginto said vessel, around said ring, common electrical connections forsaid vessel and ring, and other common electrical connections for saidanodes, saidanodes be-' mg omltted at one side to leave aineutral spaceand permit access to said ring.

17. In an electrolytic apparatus for pro ducing a metal lighter than theelectrolyte, the combination of a vessel adapted to contain suchelectrolyte in molten state and constituting the main cathode fnember, asupplemental cathode in the form of a ring supported in said vessel inspaced relation to the bottom thereof, a plurality of anodes de pendinginto said vessel around said ring, common electrical connections forsaid vessel and ring, and other common electrical connections for saidanodes, the portion of said vessel into which said anodes thus dependbeing sealed off to form a gas trap.

18. In an electrolytic apparatus for roducing a metal lighter than theelectro yte, the combination of a Vessel adapted to contain suchelectrolyte in molten state and constituting the main cathode member, asupplemental cathode in the form of a ring supported in said vessel inspaced relation to the bottom thereof, a plurality of anodes dependinginto said vessel around said ring, common electrical connections forsaid vessel and ring, and other common electrical connections for saidanodes, said anodes being omitted at one side to leave a neutral spaceand permit access to said ring, and the portion of said vessel intowhich said anodes thus depend being sealed 03 to, form a gas tra 1%. Inan electrolytic apparatus for producing ametal lighter than theelectrolyte, the combination of a vessel adapted to contain suchelectrolyte in molten state and co stituting the main cathodeamember, asupplemental cathode in the form of a ring supported in said vessel inspaced relation to the bottom thereof, means adapted to collect andconduct molten metal from the exterior' wall of said rin into theinterior thereof, a plurality of anodes depending into said vessel,around said ring, common electrical connections for said vessel andring, and other common electrical connections for said anodes.

20. In an electrolytic apparatus for. roducing a metal lighter than theelectro yte, the combination of a vessel adapted to contain suchelectrolyte in molten state and constituting the mam cathode member,asupplemental cathode in the form of a mug sup.-

ported in said vessel in spaced relation to v said ring, respectively,into the interior of said ring, a plurality of anodes dependinginto-said vessel around said ring, common electrical connections fors'aidvessel and ring, and other common electrical connections for saidanodes. j

21. In anelectrolytic apparatus for producing a metal lighter than theelectrolyte, the combination of-a vessel adapted to contain suchelectrolyte in molten state, a cathode in the form of a ring supportedin said vessel, said ring being arranged to permit free flowoftheelectrolyte around the lower edge thereof, a frame above saidvessel, and a plurality of anodes supported from said frame anddepending into said vessel around said ring.

22. In an electrolytic apparatus for producing a metal lighter than theelectrolyte, the combination of avessel adapted to contain suchelectrolyte in molten state, a cathode in the form of a ring supportedin sand vessel, said ring being arranged to permlt free flow of theelectrolyte around the lower edge thereof, a frameabove said vessel, aplurality of anodes supported from said frame and depending into saidvessel around said ring and means adapted to raise and lower said anodesindependently.

23. In an electrolytic apparatus for producing a metal lighter then theelectrolyte, the combination of a vessel adapted to contain suchelectrolyte in molten state, a-cathode in the form of a ring supportedin said; vessel, said ring being arranged to permit free flow of theelectrolyte around the lower edge thereof, a frame above said vesel, aplurality of anodes supported from said frame and depending into saidvessel around said ring, means adapted to raise and lower said anodesindependently, common electrical connections for said vessel and saidcathode, and other electrical connections to each anode.

24. In an electrolytic apparatus for producing a metal lighter than theelectrolyte, the combination ofacathodehavingasubstantially verticalactive surface and a downwardly directed trough-like projection at theupper part of said active surface to collect molten metal risingtherefrom.

25. In an electrolytic apparatus for producing a metal lighter than theelectrolyte, the combination of a. vessel adapted to contain suchelectrolyte in molten state, a hollow cathode member supported in saidvessel in spaced relation from the bottom thereof and being provided onthe outer surface adjacent to its upper end with a downwardly directedtrough-like projection and with ports from such trough permitting flowof molten metal ten metal rising from such active cathode surfaces, aplurality of anodes deipending into the space between said vessel ansupplementary cathode, common electrical connections for said principaland supplemental cathodes and other common electrical connections forsaid anodes.

28. In an electrolytic apparatus for producing a metal lighter than theelectrolyte, the combination of a vessel adapted to contain suchelectrolyte in molten state and constituting the principal cathodemember, a suppleme'ntal hollow cathode member supported in said vesselin spaced relation from the bottom thereof and forming a oollectin wellfor the metal produced in the electrolysis, the inner surface of saidvessel and the outer surface of said hollow cathode being rovided with adownwardly directed troughike projection at the u per end of the activeportion thereof adapte to entrap molten metal rising from such activecathode surfaces, means for conducting molten metal from said troughsinto said collecting well, a lurality of anodes depending into the spacetween said vessel and supplemental cathode, common electricalconnections for said principal and supplemental cathodes and othercommon electrical connections for said anodes.

Signed by us this 1st day of August, 1927.

- LOUIS E. WARD.

RALPH M. HUNTER.

therefrom into the interior of said cathode,

and a plurality of anodes depending into, said vessel around saidcathode.

26. In an electrolytic apparatus for producing a metal lighter than theelectrolyte, the combination of a vessel adapted to contain suchelectrolyte in molten state and constituting the principal cathodemember, a supple mental hollow cathode member supported in said vesselin spaced relation from the bottom thereof, a plurality of anodesdepending into the space between said vessel and supplemental cathode,common electrical connections for said principal and supplementalcathodes and other common electrical connections for said anodes.

2'11. In an electrolytic apparatus for producing a metal lighter thanthe electrolyte, the combination of a vessel adapted to contain suchelectrolyte in molten state and constituting the principal cathodemember, a supplemental hollow cathode meinber supported in said vesselin spaced relation from the bottom thereof, the inner surface of saidvessel and the outer surface of said hollow cathode being provided witha downwardly directed trough-like projection at the upper end of theactive portion thereof adapted to collect mol

